Abstract

We have constructed optimized high Tc YBa2Cu3O7(YBCO) multiturn flux transformers using laser‐deposited films patterned with ion milling and only photolithographic masking. A five‐turn flux transformer with a 0.5×0.5 mm2 pickup loop was coupled to a YBCOsuperconducting quantum interference device(SQUID) made on a separate substrate to demonstrate a prototype high TcSQUID magnetometer with all components working at 77 K. There was no additional noise associated with the input coil and transformer. The magnetic field sensitivity of the 0.5×0.5 mm2 magnetometer was 3.8 pT/√Hz at 77 K and 1 kHz.